Locaton of focus adjustment screws on a57?

Started Dec 24, 2012 | Discussions thread
digititus Senior Member • Posts: 1,568
Re: Read this before you do anything!

rpenmanparker wrote:

digititus wrote:

Backfocus can be real or percieved, but with the lenses you are using to do your testing, there is a very good chance it is not real.

Read the explanation from David Kilpatrick on perceived backfocus with fast lenses. Here is a link:


I might add that I have an A77 and the Sony 50mm f1.4 lens. Microadjusting the focus on this lens is an exercise in frustration, proabably for all the reasons David gives.

You're right, this is an excellent article and a must for someone suspecting AF error. But let me ask you this: supposing all that is wrong is the normal operation of AF overshooting or settling on the wrong spot for some built in reason. Is there any reason that offset can't be zeroed out by adjustment? Not because the lens is faulty; just because the average error is predictable and can be offset to give perfect (average) AF focusing. Why just throw up our hands and say, "That is how AF works?"

As it happens my four lenses all show back focusing on my A57 no matter which direction the focusing is occuring, i.e. either from infinity to focus or from closest setting to focus. So this is not overshoot else I would see back focusing coming from close focus and front focusing coming from infinity. The lenses are the beercan Minolta 70-210mm f/4, Tamron 17-50mm f/2.8, Tamron 28-75mm f/2.8, and Minolta 50mm f/1.4.

Is there any reason except low expectations not to send the camera to Sony for a look-see.



Given David's explanation, I would run some tests with a slower lens, or one of your lenses stopped down to f5.6. See if anything changes. If not I'd have Sony take a look. That will only cost you shipping one way, and the loss of your camera for a week or two. I would not mess with the A57's adjusting screws. I've done an A200 that way, but those screws were easy to get to.

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